A new engine for fall---

[Brian Rupnow]

My heart rate and blood pressure have returned to normal, now that I am completely finished with my version of the Nemett Jaguar. I don't WANT to build anything else until fall.
  Then I want to build a totally new engine that is not a modified version of some one else's design. Oh, it will still have all the standard things, --piston, con rod, crankshaft---you get the idea.
---I am very interested in the gearless engines, just because of how different they are. I have also learned from Malcolm Stride and whoever (Mr. Webster, I assume) designed the Webster engine. I really like that cantilevered crankshaft design as used in the Lynx and the Webster--it so greatly simplifys the crankshaft manufacturing. There is also the big plus that with a gearless type engine and an "atmospheric" intake valve, no camshaft or camshaft bearings are required.
   I won't build another engine with a wet sump and splash oiling, because it is simply too difficult to keep track of the oil level once the sump is all buttoned up.  I have been doing some research, and in addition to "sealed for life" ball bearings, one can also purchase "sealed for life " needle roller bearings and sleeves. In my mind, these would be almost perfect--sealed ball bearings for the crankshaft and sealed needle roller bearings for the big and little ends of the con rod.
   I probably won't try and use cast iron rings again. I have proven to myself that yes, I can make them, but it is a very "chancy" operation, and even when working at their best, they don't give the compression that a Viton o-ring does.
   I have proven to myself that old style points type ignition is both cheaper and far less susceptible to damage than the new electronic ignitions, but they are bulky and take up a lot of room compared to a magnet and pick-up, so the jury is still out on which I will use.
--I like the hit and miss style of engines, because there is a bit more neat mechanism available to see operating, and the real big plus is that these engines run extremely cool because of the fact that when in "miss" cycle they constantly circulate room temperature air thru the cylinder which keeps it cool.
--I would use a cast iron cylinder, and possibly a cast iron piston, as this will be a slow revving engine so the inertial weight of the piston won't be that big a deal.
---After designing and building the "Rupnow Engine" and seeing that it wants to levitate at any speed above 50 RPM I will definitely find a way to balance the crankshaft with bolt on weights.
   That all for now. If any of you fellows know of any real nifty "gearless" mechanisms, please let me know. I have plans here for the Philip Duclos style gearless engine, also for the old "star wheel" type as seen on full size hit and miss engines, and the nifty one that Myrickman posted on Modelenginemaker forum. I would be interested in any other gearless designs that I am not aware of.----------------Brian rupnow

[collbee]

Hi Brian,

Are you aware of "The Maverick".  3/4" bore. No rings. Gears have been eliminated. Exhaust valve cam mounted directly onto the crankshaft. No water-jacket. No cooling fins. Hit and miss. 

Not sure of its author but I think it may also be by Duclos. I do have a copy.

Collbee.

[Brian Rupnow]

Star wheel mechanisms and elliptical cam mechanisms both work great on gearless engines full size, but neither of them scale down very well to model engine size.

[Brian Rupnow]

On the Maverick engine, it looks like there may be a tiny star wheel right out at the end of the long rocker arm, just below the valve.
http://www.craftsmanshipmuseum.com/images/Duclos09b.jpg

[cfellows]

I've seen several of these Maverick engines at shows and none of them, in my opinion run really well.   Probably has nothing to do with their valve actuating mechanism and might just be their smaller size, but they seem to run too fast or they don't keep running.  I think this engine has a 3/4" bore.

Chuck

[Brian Rupnow]

Chuck--I have reached the conclusion that single cylinder engines of 3/4" bore or less simply don't run as well as the 7/8" or 1" diameter cylinder engines.----Brian

[Brian Rupnow]

I have been doing some more thinking on this engine "to be". Since all of my previous engines have been overhead valve types, or with valves mounted outside the cylinder ala Webster, I think I will try a side valve engine. This has the valves arranged similar to the old flathead Ford engines, with a plain flat cylinder head which has only a sparkplug hole in it, and the valves set off to one side of the cylinder with the stems pointed down toward the crankshaft (or camshaft). A good example of a side valve engine is the Philip Duclos gearless engine. I also have been thinking about ignition points. On all of my other engines they are exposed and stick out like a sore thumb. I am wondering if they couldn't be hidden in a cavity cut into one side of the flywheel similar to the old early Briggs and Stratton engines.

[cfellows]

I have been doing some more thinking on this engine "to be". Since all of my previous engines have been overhead valve types, or with valves mounted outside the cylinder ala Webster, I think I will try a side valve engine. This has the valves arranged similar to the old flathead Ford engines, with a plain flat cylinder head which has only a sparkplug hole in it, and the valves set off to one side of the cylinder with the stems pointed down toward the crankshaft (or camshaft). A good example of a side valve engine is the Philip Duclos gearless engine. I also have been thinking about ignition points. On all of my other engines they are exposed and stick out like a sore thumb. I am wondering if they couldn't be hidden in a cavity cut into one side of the flywheel similar to the old early Briggs and Stratton engines.

There's a number of side valve model engines from earlier days.  The Whippet



and I found this one which looks like a bar stock version...



This is also an interesting model although it's an F-head.  Still a nice looking engine...

http://www.deansphotographica.com/machining/engines/gas/gas.html

Chuck

[Brian Rupnow]

Chuck--Since you have already posted some good pictures of side valve engines, I am going to ask this question here as well as in its own separate thread. I have a question about side valve engines. I have looked at a number of pictures of side valve engines, and they seem to fall into two categories. One is as per the Philip Duclos Gearless engine, where the cylinder is a plain bore separate part and the combustion chamber is actually in the head, which bolts to the top of the cylinder. The valve cages, seats, and housings bolt onto the outside of the head and are connected to the combustion chamber in the head through passages drilled through the sides of the head. The piston does not travel up into the head, but stops flush with the top of the cylinder.
    T he other type, (and I'm really not sure about this) seem to have a plain bore cylinder, then a separate piece with the combustion chamber and valves buried in it bolted to the top of the cylinder, and then a flat, rather featureless (except for sparkplug hole and cooling fins) head bolted to the top of this intermediate piece.
It kind of LOOKS like the piston would have to travel up part way into this intermediate piece, but I just can't imagine a bolted joint that the piston and rings would have to travel over. (see picture) ----Or--is it possible that there is a cast iron liner that fits down through the intermediate piece and the cylinder so the piston can travel all the way without passing over a joint? Who can set me straight on this.----Brian

[IanR]

The engine you've posted a pic of, by Len Mason is the same in principle as the 2 Chuck showed, I think. The combustion space is a recess in the head, covering half the bore area and over the valves.
An alternative was used in Edgar Westbury's Kinglet and some veteran motorcycle engines, where the valve guide housing is cast into the head, and small covers are placed over each valve to allow them to be removed. I expect this would be more difficult to make in model sizes.

[Brian Rupnow]

I've got something on the go here. Have decided for the moment to forget about gearless. We're talking air cooled, 4 cycle, two independent gear driven cams---Can't really call them camshafts. All sealed ball bearings on two piece crankshaft. (two on each side) Sealed roller bearings on both ends of con rod (thus the two piece crankshaft). The combustion chamber is totally in the head. The valves set in their own housings which bolt onto the side of the head. I haven't got the tappets nor tappet guides in there yet, nor a carb or exhaust. Heck, I haven't even got fasteners in there yet!! The ignition points will set on the outside of the plate opposite side from the flywheel. May be just an exercise in time killing, but it looks interesting.

[Roger B]

Looks a nice concept  My only question would be how well the combustion chamber will purge with the separate valve chambers. I can forsee a lot of exhaust gas being left in the inlet valve chamber, especially at the planned low speeds.

[Brian Rupnow]

Roger--I don't know how big a problem that would be. What is an even greater problem is the fact that it leaves no room for a head bolt, and the added length of the passages will drop the compression ratio below what I want it to be.  I think I will look at this some more, and perhaps try making the combustion chamber and cylinder and head 3 separate pieces with a cast iron liner inside the combustion chamber and cylinder.

[Jasonb]

Brian, could you not make teh head "D" shaped a bit like the Jaguar and get the two valve blocks side by side with room for a bolt between the two. Or even a single valve block with two valves in it.

Not sure if it needs the L shaped blue base unless you like making swarf  , could the base not be flat with the olive end support fixed like the other two grey ones?

J

[Brian Rupnow]

Okay--We'll put my previous attempt down as  not really feasible---. Try again!! I think this is doable---but that cylinder would be an absolute monster to machine. The only thing I see that isn't really workable in this drawing is that the flange on the bottom of the cylinder will foul any tappets coming up directly under the valve stems. Even though I show the valves seating in the aluminum cylinder, remember, this is just a layout to see if I can get all the pieces into an envelope of the required size. If I did go ahead with this, I would machine valve cages and press/Loctite them into holes in the cylinder in the same position.